This application relates to improved antioxidant, antiwear/extreme pressure additive compositions and lubricating compositions containing the same.
In U.S. Pat. No. 4,880,551, there are provided synergistic antioxidant compositions containing (a) 1-[di(4-octylphenyl)aminomethyl]tolutriazole and (b) an antioxidant selected from the group consisting of methylenebis(di-n-butyldithiocarbamate), 2,6-di-t-butyl-4-sec-butylphenol, 2,6-di-t-butyl-4-methylphenol and butylated phenol mixture and wherein the ratio of the tolutriazole compound to the antioxidant ranges from about 1:4 to about 4:1.
Surprisingly, it has been discovered that methylenebis(di-n-butyldithiocarbamate) when used in conjunction with a diphenylamine derivative of tolutriazole or benzotriazole (henceforth xe2x80x9cbenzotriazole derivativexe2x80x9d) at a ratio of above about 4:1 to about 50:1, show similar synergistic effect with respect to antioxidant activity as the antioxidant compositions disclosed in U.S. Pat. No. 4,880,551 with ratios of 1:4 to 4:1 but with improved antiwear/extreme pressure (EP) performance in lubricants.
A first embodiment of the invention is an antioxidant composition with improved antiwear/extreme pressure performance which comprises: (a) methylenebis(di-n-butyldithiocarbamate) and (b) a diphenylamine derivative of tolutriazole or benzotriazole wherein the (a):(b) mass precent ratio ranges from above about 4:1 to about 50:1.
A second embodiment of the invention is an antioxidant composition with improved antiwear/extreme pressure performance containing methylenebis(di-n-butyldithiocarbamate) and a diphenylamine derivative of tolutriazole or benzotriazole at a ratio of about 5:1 to about 40:1.
A third embodiment of the invention is an antioxidant composition with improved antiwear/extreme pressure performance containing methylenebis(di-n-butyldithiocarbamate) and a diphenylamine derivative of tolutriazole or benzotriazole at a ratio of about 11.3:1 to about 38:1.
Another embodiment of the invention relates lubricating compositions having improved antioxidant, antiwear and extreme pressure properties which comprise a major portion of an oil of lubrication viscosity and oxidation inhibiting amount of the antioxidant composition of the invention.
Additionally it has been found that additional tolutriazole and benzotriazole derivatives are effective.